I am planning to buy a Nikon D80 with 18-135 kit lense and a Nikkor 70-300. I take a lot of wildlife and nature shots. I need some advise on what I need to take closeup pictures of insects. I like to be 2-3 ft away if possible. I don't know whether it is better to go macro lense, extension tubes or closeup lense. If the lenses above are bad choices, give me some better ones. I am trying to keep the entire purchase under $2000. Thanks in advance.